RedCardinal - 4:30 pm on Sep 5, 2008 (gmt 0)

.ie showing in .co.uk, vice-versa, and switching between the two is usually a sign of dupe filters not being sure which version is the authority.

May be that your boilerplate is too similar, and the content on the pages tripping the filter is quite thin?

One other thing - .co.uk pages on google.ie seems also to be some sort of issue Google is having with geotargeting.

Last idea no one has floated - have you had any outages recently?